Sorry no one bothered to reply but I have a clue as to why. I used the search function (located in the upper right-hand corner of the VLC forum page) and entered 'subtitles not working'. I got
774 matches, which means this is a known issue. Sometimes it appears to be a problem with VLC and sometimes it appears to be an issue with the phone or tablet you're using. Although I can't (and don't) speak for the forum moderators, I would guess that they get a little tired of commenting on the same topic over and over again.
If my reply here today doesn't generate any helpful feedback from others, my best advice would be to download the latest
beta version of VLC, which you can find here:
https://nightlies.videolan.org Fyi: Beta versions are cool because 1) they contain bug fixes and 2) they often contain new features, not found on the standard releases you would get by downloading it from Playstore.
When you click on the above link, you will have to select from one of these:
Android (ARMv7-A)
Android (ARMv8-A)
Android (x86)
Android (x86_64)
Android (mips)
Android (mips64)
I'm not sure which one of the above is best for your Samsung Galaxy Tab but I'm sure you can find out. Maybe someone here will pop in and tell us
If that doesn't solve the problem, hang in there and try to be patient. They are aware of the problem(s) with subtitles.
Kent F. Kruhoeffer